YASC does have a duplicates function. I used it and determined all the puzzles in Boxxle 1 & 2, Perfect and Revenge that are considered duplicates of the original 50 as contained in my tribute file, which contains all 64 variants of the 50. I will be matching them up visually today for a complete comparison.

I did a visual comparison of the Boxxle 1 & 2, Perfect and Revenge files that I downloaded here against the ones supplied by Mark in this thread. Except for the missing puzzles in the download versions of Perfect and Revenge here, they are the same files.

Now I can be assured that I am dealing with the actual puzzles as distributed by Thinking Rabbit, and I don't have to be concerned about the versions of Boxxle on the Sokoban Online site.

Thank you Mark for your assistance with the files. Thank you Ben for pointing me towards SokoDup, even though it will not run under Vista. Thank you Bjorn for this site and this forum. I may complain alot as far as you and some others may be concerned, but I do value this site and the people that use it. Keep up the good work.

Mark, I think you should verify the level against the real gameboy game before claiming that it's really correct.

You are right, but we are not playing gameboy. There is also a PC sokoban-like game called cheese-terminator, where the mouse is pushing the cheese instead of boxes. That's where I've first seen some of the boxxle levels and some are again flipped and some not. So it is very difficult, what is "flipped" and what not.

It is just a matter what a certain player has seen first. (For me the gameboy version is flipped upside down). The boxxle that you will get on the internet (and that everyone is playing) is not compatible with the gameboy version:
http://www.letslogic.com/pack_info.php?id=9

The only logical thing is, that Thinking Rabbit decided to reuse the same levels in multiple collections, and that they decided to change their orientation based on the "platform". The authors probably didn't care, since this is the same level, flipped or not.

If you (for some unknown reason) want to have it compatible with gameboy version, than you would need to make orientation edits.

For the game boxxle and boxxle II, it is only released for Nintendo gameboy. Boxxle wiki claimed that it is released for Sega game gear, that is wrong. For Sega game gear, that's a different game name with mixed levels from boxxle and boxxle II. You can check sokoban.jp for the official list. Perfect and Revenge are different, that's released for many platforms and some platforms has slightly differences. For boxxle， no exception， Nintendo gameboy only.

@ben. I ran it according to the instructions and got a side-by-side error. There is no available fix for this error so far as sokodup is concerned, so I have no idea how to make it run. If you have some idea as to what to do about this error, please inform me.